I wear 5.11 tactical pants. They have reinforced knees, not pads, but they're pretty tough. I think paintball pants are pretty overrated, I play just as well in 5.11's as I do in dye c6's. Also, you can wear 5.11 everywhere so they're pretty cost effective.

Been wearing Exalt's Throwback pants for the majority of my practice/recball lately, for $60 new they're pretty nice. Only thing is they've got no padding, so you've got to wear knee pads and/or slider shorts underneath if you want that extra protection.